Referring to FIG. 7, a prior art filter is illustrated. The prior art filter has a filter box 70 at one side of a receptacle 7. The filter box 2 is installed with a resistor 71, an inductor coil 72, Y capacitors 73, and other electronic elements. A cover 700 serves to seal the electronic elements within the filter box 70. A positive electrode 74, a negative electrode 75 and a ground sheet 76 are protruded from one side of the filter box 70. A metal casing 8 serves to enclose one side of the receptacle 7 and the filter box 70 so that the positive electrode 74, the negative electrode 75 and the ground sheet 76 protrude out of the metal casing 8.
However, in this prior art, the positive electrode 74, the negative electrode 75 and the ground sheet 76 protruding out of the metal casing 8 are welded to a circuit board with a larger space so as to affect the installation of other elements of the circuit board. Furthermore, if two ends of a conductive wire is directly connected to the circuit board, the positive electrode 74, the negative electrode 75 and the ground sheet 76 so as to improve the problem of occupying a larger space in the circuit board, but the problem of electromagnetic interference induces. As a result, the filter will be unstable.